Silicone rubbers are often used as mold forming materials for molding a variety of cast articles of plastics including polyesters, polystyrene, rigid urethane foams, epoxy resins and others. Silicone rubber molds have excellent inherent release properties so that cast articles can be readily removed from the mold. The silicone rubbers can be flexed and stretched so that articles with mold undercuts can be easily removed from the molds. However, such molds must be flexed and stretched very gently or mold tearing occurs since tensile strength of silicone rubbers is normally low. Moreover, silicone rubber materials are comparatively expensive resulting in expensive molds.
Silicone rubbers and silicone resins are widely used commercially for a wide variety of purposes including electric insulation, sealing means, coating applications and the like in addition to use as mold materials. In such applications it is often desirable to bond the silicone rubber to other materials in order to increase tensile strength or to otherwise protect the silicone materials. However, this has been difficult in the prior art. Bonding methods are known for bonding silicone rubber and silicone resins to other polymers as when the silicones are cast onto polymeric surfaces and then cured in place. However, no commonly acepted methods are well-known for forming effective bonds when bonding silicone rubber and silicone resins which have already been cured, to other polymeric materials. This is true even though effective bonding means have been developed for bonding cured siloxane resin surfaces to other cured siloxane resin surfaces as disclosed in U.S. Pat. No. 3,698,982 issued Oct. 17, 1972.